There is known a diagnosis unit as a tool for diagnosing a failure of a vehicle such as automobile. In recent years, there is considered that a so-called expert system for registering information on failures occurring in the past in database and estimating a cause of a newly occurring failure is used for a diagnosis machine. The expert system includes a rule base estimation system in which human experience knowledge is registered in database for retrieval and a model base estimation system in which behaviors of the system during normal time or failure are learned for retrieving a failure cause via simulation.
In the former system, a mechanism is simple and a relatively high reliability can be expected but the knowledge is difficult to rule and a rule needs to be added or modified each time the target system is changed.
On the other hand, in the latter system, even if an operating staff does not have sufficient experience or knowledge, a failure site can be estimated and a certain degree of versatility can be expected in terms of the change in the target system. Particularly, a method for comparing data during normal time with data during failure under the same driving environmental condition is one of the most effective means for finding a cause of a failure.
However, since various environmental conditions or travel patterns are present for the driving of a vehicle and a range of normal values, which a large number of respective driving parameters can take depending on a respective situation, can be independently changed, the data during normal time needs to be collected under various driving situations in order to obtain normal value data for comparing items of data under similar conditions and to make an accurate decision.
For the purpose, a dedicated test vehicle provided with a driving data accumulation unit is utilized for conducting a large amount of travel tests, and data collection and accumulation needs a lot of labor.
Japanese Patent Application Laid-Open No. 62-261938 Publication (Patent Literature 1) describes therein a diagnosis unit comprising a knowledge data storing means for storing accurate information on a relationship between a symptom of a failure and a cause thereof, and a rare case storing means for storing inaccurate information.
Japanese Patent Application Laid-Open No. 6-95881 Publication (Patent Literature 2) describes therein analyzing design data or past failure data and inputting it as EMEA in a positive estimation system in relational database, creating a modified EMEA and then an event sequence diagram, creating a failure retrieval three for reference to a rule base, and digitizing an expert know-how to create a rule base.